Anode Material, Negative Electrode Plate and Secondary Battery

The subject application claims priority under 35 U.S.C. § 119 to Chinese Patent Application No. 202411381391.6, filed on Sep. 29, 2024. The entire disclosure of Chinese Patent Application No. 202411381391.6 is incorporated by this reference.

The present application relates to the field of electrochemical energy storage, and specifically relates to an anode material, a negative electrode plate and a secondary battery.

Silicon anode materials have higher theoretical energy density, and thus are generally considered to have the potential to improve properties of lithium-ion batteries. Existing silicon materials are usually compounded with metals, oxides, organic polymers, carbon and other materials to obtain anode materials with better electrical conductivity and a lower expansion effect. For example, the anode materials based on amorphous silicon and a carbon matrix are considered to have the advantages of high initial efficiency, high capacity, low expansion and good cycle stability. However, it has been found in practice that such kind of materials have the problem of easy falling of a surface coating layer, resulting in lower expansion performance and capacity of the materials than expected and deterioration of properties of the materials.

In view of the aforementioned content, the present application provides an anode material to solve at least one of the above problems.

To achieve the above objective, the present application provides an anode material. The anode material includes a core body and a carbon coating layer that coats at least a partial surface of the core body, and the core body includes a matrix and an active substance. A 10-day gas production A of the anode material is less than or equal to 100 mL/kg. A residual carbon rate of the anode material is defined as

and the residual carbon rate γ is less than or equal to 20%. A method for testing the 10-day gas production A includes: placing 50 g of the anode material in 300 mL of a slurry mixing tank, adding 50 g of sodium carboxymethyl cellulose with a mass fraction of 5% and 100 mL of pure water into the mixing tank, conducting stirring at a stirring frequency of 50 Hz for a stirring time of 1 h to obtain a slurry, placing the slurry in an aluminum-plastic film, and measuring the 10-day gas production A of the slurry by a drainage method. A method for testing mincludes: placing the anode material in a slurry mixing tank for stirring at a stirring frequency of 50 Hz for a stirring time of 1 h, removing the stirred anode material with a mass of m, placing the stirred anode material in a hydrofluoric acid solution with a mass fraction of 20% for soaking for 1 h, removing the soaked anode material, and measuring the soaked anode material after cleaning and drying to obtain a mass of m. A method for testing mincludes: placing the anode material with a mass of min a hydrofluoric acid solution with a mass fraction of 20% for soaking for 1 h, removing the soaked anode material, and measuring the soaked anode material after cleaning and drying to obtain a mass of m.

In some possible embodiments, the 10-day gas production A of the anode material is 3 mL/kg to 85 mL/kg.

In some possible embodiments, the residual carbon rate γ of the anode material is 3% to 16%.

In some possible embodiments, a powder conductivity of the anode material at 20 kN is 0.5 S/cm to 9.5 S/cm.

In some possible embodiments, a powder conductivity of the anode material at 20 kN is 0.5 S/cm to 4.5 S/cm.

In some possible embodiments, an ID/IG of the anode material is 0.5 to 5.0.

In some possible embodiments, a specific surface area of the anode material is less than or equal to 5 m/g.

In some possible embodiments, a total pore volume of the anode material is 0.001 cm/g to 0.1 cm/g.

In some possible embodiments, a compaction density of the anode material is 0.8 g/cmto 1.2 g/cm.

In some possible embodiments, the anode material includes micropores, mesopores and macropores, and based on the total pore volume of the anode material, a volume proportion of the micropores is less than or equal to 5%, a volume proportion of the mesopores is 87% to 97%, and a volume proportion of the macropores is less than or equal to 13%.

In some possible embodiments, a particle size D10 of the anode material is 1 μm to 5 μm. In some possible embodiments, a particle size D50 of the anode material is 6 μm to 16 μm. In some possible embodiments, a particle size D90 of the anode material is 16 μm to 24 μm.

In some possible embodiments, an average pore size of pores of the anode material is 0.5 nm to 20 nm.

In some possible embodiments, a thickness of the carbon coating layer is 0.1 nm to 1,000 nm.

In some possible embodiments, a thickness of the carbon coating layer is 10 nm to 1,000 nm.

In some possible embodiments, the active substance includes one or more of Si, Sn, Ge, Pb, Ag, Mg, Zn, Ga, In, Sb, Bi, and alloy materials thereof.

In some possible embodiments, the active substance includes a silicon material, the silicon material includes silicon particles, and the silicon particles include one of amorphous silicon, crystalline silicon and a composite of crystalline silicon and amorphous silicon.

In some possible embodiments, the silicon material includes at least one of a silicon oxide and a silicon alloy.

In some possible embodiments, the silicon material includes silicon particles and silicon oxide layers located on surfaces of the silicon particles, and the silicon oxide layers include silicon oxides.

In some possible embodiments, an average particle size of the active substance is 0.1 nm to 500 nm.

In some possible embodiments, the active substance includes a silicon material, the silicon material includes silicon particles, and the silicon particles include amorphous silicon.

In some possible embodiments, the active substance includes a silicon material, the silicon material includes at least one of a silicon oxide and a silicon alloy.

In some possible embodiments, the active substance includes a silicon material, the silicon material includes silicon particles and silicon oxide layers located on surfaces of the silicon particles.

In some possible embodiments, the silicon oxide layers include silicon oxides, a general formula of the silicon oxides is SiOx, wherein 0.5≤x<2.

In some possible embodiments, calculated with a mass of the silicon material as 100%, a mass percentage content of oxygen atoms in the silicon material is 1% to 18%.

In some possible embodiments, a total pore volume of the matrix is 0.5 cm/g to 2.0 cm/g.

In some possible embodiments, a specific surface area of the matrix is 600 m/g to 3,000 m/g.

In some possible embodiments, the matrix includes a carbon matrix, and the carbon matrix includes one or more of amorphous carbon, graphitized carbon, a mesophase carbon microsphere, and a carbon gel.

In some possible embodiments, the matrix includes a non-carbon matrix, and the non-carbon matrix includes one or more of a metal oxide, a silicide, a silicate, a phosphate, a titanate, and an aluminum borate salt.

In some possible embodiments, the matrix of the anode material includes a carbon matrix, the active substance of the anode material includes a silicon material, and based on the mass of the anode material, a mass proportion of element carbon of the anode material is 40% to 60%, or a mass proportion of element silicon of the anode material is 35% to 55%.

The present application further provides a negative electrode plate, which includes a negative current collector and a negative active material layer arranged on the negative current collector, wherein the negative active material layer includes the aforementioned anode material.

The present application further provides a secondary battery, which includes the aforementioned negative electrode plate.

In the present application, by arranging the carbon coating layer on at least a partial surface of the core body, the carbon coating layer can achieve a protective effect on the core body, which decreases the gas production A of the anode material and is also conducive to reducing the expansion of the anode material in a cycle process, thereby improving the cycle stability of the secondary battery based on the anode material. Meanwhile, on the premise that the anode material has a certain carbon coating amount to reduce the gas production, the residual carbon rate γ of the anode material is less than or equal to 20%, so that a compaction degree of the carbon coating layer is also higher, carbon atoms are closely arranged, and convenience is provided for forming sufficient conductive channels and transmitting electrons in the carbon coating layer to maintain great electrical conductivity. A material with high electrical conductivity usually has better ion conductivity, which is conducive to reducing the internal resistance of the battery and improving the charge efficiency and discharge efficiency, thereby facilitating the improvement of the capacity and initial coulombic efficiency of the obtained secondary battery.

Examples of the present application are described in detail below. The examples described below with reference to the drawings are illustrative, which are intended only to interpret the present application and shall not be construed as limitations to the present application. It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meanings as generally understood by those skilled in the technical field of the present application. The embodiments and features in the embodiments of the present application can be combined with each other without conflict. Many specific details are set forth in the description below to facilitate a full understanding of the present application, and the embodiments described are only a part of the embodiments of the present application, rather than all of the embodiments.

Anode materials obtained by compounding silicon materials and carbon materials have excellent electrochemical properties. For example, amorphous silicon carbon materials have the advantages of high initial efficiency, high capacity, low expansion and great cycle stability. However, coating layers on surfaces of the amorphous silicon carbon materials are prone to falling, resulting in deterioration of properties of the materials. Therefore, how to prepare low-expansion and high-capacity silicon-carbon composite materials with stable outer coating layers has become one of development directions of the anode materials.

The present application has found in research that improving preparation processes of the anode materials is conducive to achieving coating layers with better compactness, so as to achieve the purpose of reducing falling of the coating layers on the surfaces of the anode materials.

Based on this, an embodiment of the present application provides a secondary battery, which includes a shell, an electrode assembly and an electrolyte. The electrode assembly and an electrolyte solution are both located in the shell.

The shell may be a packaging bag that is obtained by encapsulation with an encapsulation film (e.g., an aluminum-plastic film), for example, a pouch battery. In other examples, the secondary battery may also be a steel shell battery, an aluminum shell battery, etc.

Referring toor, the electrode assemblyincludes a positive electrode plate, a negative electrode plateand a diaphragm, and the diaphragmis arranged between the positive electrode plateand the negative electrode plate. When the electrolyte solution is arranged (not shown in the drawings), during charge, referring to, active ions (e.g., lithium ions) are disembedded from lattices of a cathode material (e.g., a lithiated intercalation compound) of the positive electrode plate, pass through the diaphragmthrough the electrolyte solution to reach the negative electrode plate, and then are inserted into lattices of an anode material. During discharge, referring to, the active ions (e.g., lithium ions) are disembedded from the lattices of the anode material of the negative electrode plate, pass through the diaphragmthrough the electrolyte solution to reach the positive electrode plate, and then are inserted into the lattices of the cathode material (e.g., a lithiated intercalation compound). Generated electrons reach the positive electrode platefrom the negative electrode platethrough an external circuit, and an electric current is formed by reverse movement of the electrons and can be used by electrical appliances.

In some examples, the electrode assemblymay be of a laminated structure, which is formed by sequentially and alternately laminating the positive electrode plate, the diaphragmand the negative electrode plate. In other examples, the electrode assemblymay also be of a winding structure, which is formed by sequentially laminating and winding the positive electrode plate, the diaphragmand the negative electrode plate.

The positive electrode plateincludes a positive current collector and a positive active material layer arranged on at least one surface of the positive current collector. The positive current collector may use aluminum foil or nickel foil, etc., and may also be any composite current collector disclosed in the prior art, for example, but not limited to, a current collector formed by combination of the aforementioned conductive foil and a polymer substrate. The positive active material layer includes an active cathode material, and the active cathode material includes a compound capable of reversibly embedding and disembedding lithium ions (i.e., a lithiated intercalation compound). In some examples, the active cathode material may include a lithium transition metal composite oxide. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese and nickel. In some examples, the active cathode material may include, but is not limited to, at least one of lithium cobaltate (LiCoO), a lithium nickel-manganese-cobalt ternary material (NCM), lithium manganate (LiMnO), lithium nickel manganate (LiNiMnO), or lithium iron phosphate (LiFePO).

The positive active material layer further includes a binder, which is used for bonding active cathode material particles to facilitate the formation of a membrane layer and can also improve the binding force between the positive active material layer and the positive current collector. In some examples, the binder may include, but is not limited to, at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylideneoxy-containing polymers, polyethylene pyrrolidone, polyurethane, polytetrafluoroethylene, poly(1,1-vinylidene difluoride), polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene rubber, epoxy resin, or nylon, etc.

The positive active material layer may further include a conductive material, and the conductive material includes, but is not limited to, a carbon-based material, a metal-based material, a conductive polymer, or any combination thereof. In some examples, the carbon-based material may include, but is not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, a carbon fiber, or any combination thereof. In some examples, the metal-based material may include, but is not limited to, a metal powder or a metal fiber, such as copper, nickel, aluminum, or silver. In some examples, the conductive polymer may be a polyphenylene derivative.

The negative electrode plateincludes a negative current collector and a negative active material layer arranged on at least one surface of the negative current collector. The negative current collector may use at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or a carbon-based current collector, etc., and may also be any composite current collector disclosed in the prior art, for example, but not limited to, a current collector formed by combination of the aforementioned conductive foil and a polymer substrate.

The negative active material layer includes an anode material, the anode material includes a core body and a carbon coating layer that coats at least a partial surface of the core body, and the core body includes a matrix and an active substance. A 10-day gas production A of the anode material is less than or equal to 100 mL/kg. For example, the 10-day gas production A of the anode material may be 100 mL/kg, 85 mL/kg, 70 mL/kg, 65 mL/kg, 30 mL/kg, 20 mL/kg, 5 mL/kg, 4 mL/kg, 3 mL/kg, or any value within a range consisted of any two of the above numerical values. Wherein, a method for testing the 10-day gas production A includes: placing 50 g of the anode material in 300 mL of a slurry mixing tank, adding 50 g of sodium carboxymethyl cellulose with a mass fraction of 5% and 100 mL of pure water into the mixing tank, conducting stirring at a stirring frequency of 50 Hz for a stirring time of 1 h to obtain a slurry, placing the slurry in an aluminum-plastic film, and measuring the 10-day gas production A of the slurry by a drainage method.